Bottom Line:
Pupil eccentricity was reduced by -39.56%; P<0.001.This novel investigation based on digital analysis of Scheimpflug imaging data suggests that the cataract postoperative photopic pupil is reduced and more circular.These changes appear to be more significant with increasing patient age.

Patients and methods: The study group (86 eyes, patient age 70.58±10.33 years) was subjected to cataract removal surgery with in-the-bag intraocular lens implantation (pseudophakic). A control group of 75 healthy eyes (patient age 51.14±16.27 years) was employed for comparison. Scheimpflug imaging (preoperatively and 3 months postoperatively) was employed to investigate central corneal thickness, AC depth, and AC volume. In addition, by digitally analyzing the black-and-white dotted line pupil edge marking in the Scheimpflug "large maps," the horizontal and vertical pupil diameters were individually measured and the pupil eccentricity was calculated. The correlations between AC depth and pupil shape parameters versus patient age, as well as the postoperative AC and pupil size and shape changes, were investigated.

Conclusion: Cataract extraction surgery appears to affect pupil size and shape, possibly in correlation to AC depth increase. This novel investigation based on digital analysis of Scheimpflug imaging data suggests that the cataract postoperative photopic pupil is reduced and more circular. These changes appear to be more significant with increasing patient age.

f6-opth-8-2141: Graphical illustration of the anatomical pupil, as imaged through the optical system of the cornea (not to scale).Note: The anatomical pupil is the “aperture stop,” and the magnified “apparent pupil” is the entrance pupil of the optical system.

Mentions:
The pupil size depicted by the Scheimpflug system and measured in this study corresponds to the “true” anatomical pupil size calculated from the three-dimensional model, derived by ray tracing. As stated above, pupillometry systems report the size of the entrance pupil, ie, the virtual image of the physical pupil as imaged through the cornea. In other words, traditional pupillometry employs a simple “image capture” of the pupil, which, however, corresponds to the “entrance” pupil. As in any optical system, the entrance pupil is the magnified, virtual image of the aperture stop, ie, the anatomical pupil;31 this is what any observer “sees” as a pupil, as illustrated in Figure 6. The magnification depends on the actual distance of the anatomical pupil from the cornea (approximated by the AC depth), the refractive indices (n) of the media beside the cornea, as well as the corneal refractive power. In an emmetropic eye with average total corneal power +43 D, AC depth 3.6 mm, and naqueous 1.336, the apparent pupil is about 13.1% larger and 0.55 mm closer to the cornea than the anatomical pupil.

f6-opth-8-2141: Graphical illustration of the anatomical pupil, as imaged through the optical system of the cornea (not to scale).Note: The anatomical pupil is the “aperture stop,” and the magnified “apparent pupil” is the entrance pupil of the optical system.

Mentions:
The pupil size depicted by the Scheimpflug system and measured in this study corresponds to the “true” anatomical pupil size calculated from the three-dimensional model, derived by ray tracing. As stated above, pupillometry systems report the size of the entrance pupil, ie, the virtual image of the physical pupil as imaged through the cornea. In other words, traditional pupillometry employs a simple “image capture” of the pupil, which, however, corresponds to the “entrance” pupil. As in any optical system, the entrance pupil is the magnified, virtual image of the aperture stop, ie, the anatomical pupil;31 this is what any observer “sees” as a pupil, as illustrated in Figure 6. The magnification depends on the actual distance of the anatomical pupil from the cornea (approximated by the AC depth), the refractive indices (n) of the media beside the cornea, as well as the corneal refractive power. In an emmetropic eye with average total corneal power +43 D, AC depth 3.6 mm, and naqueous 1.336, the apparent pupil is about 13.1% larger and 0.55 mm closer to the cornea than the anatomical pupil.

Bottom Line:
Pupil eccentricity was reduced by -39.56%; P<0.001.This novel investigation based on digital analysis of Scheimpflug imaging data suggests that the cataract postoperative photopic pupil is reduced and more circular.These changes appear to be more significant with increasing patient age.

Patients and methods: The study group (86 eyes, patient age 70.58±10.33 years) was subjected to cataract removal surgery with in-the-bag intraocular lens implantation (pseudophakic). A control group of 75 healthy eyes (patient age 51.14±16.27 years) was employed for comparison. Scheimpflug imaging (preoperatively and 3 months postoperatively) was employed to investigate central corneal thickness, AC depth, and AC volume. In addition, by digitally analyzing the black-and-white dotted line pupil edge marking in the Scheimpflug "large maps," the horizontal and vertical pupil diameters were individually measured and the pupil eccentricity was calculated. The correlations between AC depth and pupil shape parameters versus patient age, as well as the postoperative AC and pupil size and shape changes, were investigated.

Conclusion: Cataract extraction surgery appears to affect pupil size and shape, possibly in correlation to AC depth increase. This novel investigation based on digital analysis of Scheimpflug imaging data suggests that the cataract postoperative photopic pupil is reduced and more circular. These changes appear to be more significant with increasing patient age.